Artist Matthew Mazzotta conceived of Project Park Spark: a program that gathers dog feces, generates methane from them, and powers lights using that methane. The system is set up in a park in Cambridge, Massachusetts.

Dog owners collect their dog waste in a special biodegradable bag and throw it into the digester – an air-tight cylindrical container, where the dog faeces are broken down by anaerobic bacteria. A byproduct from that process is methane which can then be released through a valve and burnt as fuel. In this case it is being used to power an old-fashioned gas-burning lamppost in a park.